From observations on a Ribes ussuriense clone, the cultivars R. nigrum var. sibiricum 'Rus' and 'Naryadnaya' [Elegant] and progenies of the crosses Rus X Wisla [Vistula], Rus X Lepaan Musta and R. ussuriense X Rus, during 1971-1973, a distinction was established between mite resistance (found in Rus and Naryadnaya and segregating in their progenies) and reversion virus resistance or tolerance (found in Rus and some of its hybrids). Mite resistance depends upon a single dominant gene, P, which causes necrosis and shrivelling in infested buds, instead of galling.